1. Field of the Invention
The present invention relates to electronic control of compression ignition engines with electronic control modules programmable to define a range of engine speed operation having first and second thresholds, and adjusting engine operation within a range after detecting engine operation within a range between thresholds in a time interval.
2. Background Art
The many moving parts of a vehicle drivetrain or motorized machinery often induce harmonic vibrations throughout the drivetrain that can create severe vibration and stresses in the components, in the mounting structures and throughout the vehicle or machine carrying the engine. While mechanical dampers have often been employed to reduce the effect of operating the drivetrain at the speeds at which the harmonic amplification of destructive vibrations are induced, the addition of mass to the moving components or the machinery is often undesirable as such dampers may have limited effectiveness, may reduce the efficiency of the vehicle or machinery as a whole and may add to wear over the equipment""s lifetime. The removal of destructive torsional forces within the normal operating range can be quite expensive.
Moreover, none of the previously known dampers were automatically responsive to electronic control modules effecting the ignition and operation of an engine. Accordingly, an operator could operate an engine at undesirable speeds for extended periods at which the induced vibrations may be amplified by harmonics that are destructive to the engine, adjacent components and the equipment carrying the engine. Accordingly, the previously known controls for internal combustion engines did not avoid the destructive effects of operating an engine in speed ranges considered undesirable for the equipment.
The present invention overcomes the abovementioned disadvantages by providing an electronic control system for an engine that can detect engine operation in a range considered to be undesirable and can control adjustment of the engine speed to avoid the undesirable range. The response may be a generation of a signal that accelerates the engine speed above or decelerates the engine speed below the thresholds defining a range defined as undesirable. Moreover, multiple ranges or thresholds may be programmed into the control or otherwise sensed as desired to avoid undesirable engine RPM ranges without unduly affecting the function of the vehicle or machinery employing the control.
In one embodiment, the time of engine operation in an undesirable speed range is limited by an add-on circuit that detects engine operation in the range and permits the control to command an automatic pass through the range in which two engine speed outputs, one associated with each threshold speed defining the range, one speed command and one torque or speed limit control module signal are combined with two relays and diode to perform the automatic pass through. Alternatively, a single speed switch output may enable a speed command permitting the engine to accelerate to a rated speed outside of the range. Such an embodiment may be preferable where simpler circuitry is desired, and operator intervention is available, for example, to switch engine speed to a lower operating speed, for example where an Enable Idle request is triggered by the operator. Such an alternative may require digital inputs of Variable Speed Governor (VSG) Inhibit and Alternative Minimum variable speed governor (VSG) as well as a digital output, for example, Speeds Switch Output, which is preferably provided by a speed switch output or Engine Overspeed control signal.
Another embodiment, that does not rely upon discrete circuitry to interface with the electronic control, may be employed by utilizing the timer based torque limiting operation previously programmed in Detroit Diesel marine engine controls and modified by reducing the power level command to a less than desirable power level when the engine operates in a speed range determined to be undesirable. This engine overload protection normally prohibits operation at torque levels above the normal propeller load curves for a prolonged period of time by temporarily maintaining acceleration performance, while protecting engine durability by ramping down engine output to the maximum allowed torque over time.
In addition, an embodiment of the present invention may be implemented in new software. The reprogramming of previously known electronic control modules, for example, reprogramming with a calibration parameter to enable an engine Speed Range Exclusion enable or grounding a digital input when a speed signal is in a range between first and second thresholds. A set speed table may force acceleration through the upper threshold so that the engine speed remains above the upper threshold level until the requested speed signal falls below the first threshold. Regardless of the embodiment employed, the present invention avoids engine operation in an undesirable range of speeds between upper and lower threshold speeds. The detector may be simply added circuitry employed to communicate with the electronic control module, or may be derived from signals already received by an electronic control module as processed in the reprogrammed microprocessor operation. As a result, the present invention substantially reduces destructive operation and promotes a longer working life for the vehicle or machinery operated with the control.